Step-by-step explanation
Step 1
a)system diagram and Free body diagram
F.B.D.
Step 2
B)
Net force:
Let
positive to the rigth, negative to the left, so

so, the net force is 5 N (east)
Step 3
net force in the vertical direction:
as the box is not moving on the y-axis, the sum of forces equals zero, hence

so
the net force in the vertical direction is zero
I hope this helps you